Conventionally, repeater (communication repeater devices) are known, which enable the use of mobile communication terminals such as smartphones and tablet terminals in buildings, underground shopping areas, and subway yards. For example, the repeaters relay communication between a radio base station adopting time division duplexing (TDD) and mobile communication terminals.
In TDD system, such a repeater needs to output radio signals in synchronization with radio signals from a base station located in the peripheral area. Upon receipt of a radio signal from the base station, the repeater extracts timing from the radio signal in order to output radio signals in synchronization with the radio signals from the base station. Then, the repeater controls the timing at which the radio signals received from the base station are retransmitted, in accordance with the extracted timing.
For example, the repeater detects the waveform of a downlink signal that is transmitted from the base station to detect the timing at which a detected level matches or exceeds a certain threshold value, as switching timing from an uplink to a downlink.
Detecting the downlink signal as above, however, makes it difficult to accurately estimate the switching timing from the uplink to the downlink due to differences in signal level characteristics among different radios at the time of signal rising.
An object of the present invention is to provide a communication repeater device, a control method, and a computer program product that enable accurate estimation of the switching timing between the uplink and the downlink.